Since YouTube is a Google service, users you have "blocked" (preventing them from interacting with you across Google services) are stored in your central blocklist. Go directly to your Google Blocklist . Android/iOS App:
Click on (gear icon) located in the bottom-left sidebar. Select the Community tab from the left menu. Scroll down to the Hidden users section. how to unblock users on youtube
If you cannot find the "Blocked users" list via Settings, you can also unblock them by finding an old comment. Go to a video where they previously commented (or your comment history), tap their name to go to their channel, tap the three dots (⋮) in the top right, and if they are blocked, the option will say Unblock . Since YouTube is a Google service, users you